I'm just gonna choose wrestlers as I think that's what you were intending when you made the thread, however, just for the record, if I were choosing them McMahon followed by Heyman would be top by a mile.
IMO
1: John Cena - Still nobody can work a crowd like he does, always really confident delivery and I can't even remember the last time he messed up a line. Obviously his material has been pretty crap for the last 6 years but he's proved that he can be entertaining as fuck even with it.
2: Punker - He can be a bit inconsistent at times hence why he's behind Cena. When he's at his best though he is absolutely outstanding, and even when he isn't he gets shit tonnes of heat every time he goes near a microphone.
3: Dean Ambrose - Call me over the top if you wish, but I think he's that good. He's got the best voice for promos in the entire WWE IMO, and his mannerisms are always perfect. I guess the only flaw I can find with him is that he did have a tendency to ramble slightly in the older promos of his that I've watched. I know it's just a character thing but just something I've picked up on.
4: Damien Sandow - He has an incredibly hard role to play, one off day could shatter the illusion of his entire character. He has to use a ridiculous vocabulary and basically not fuck up on any lines which he has done really successfully so far. So much fun.
5: Dolph Ziggler - I've said it loads of times now, but he doesn't suit heel mic work. If he turned face he could be awesome but I just know they would give him a character change and that would suck. His quick talk, his wit, his natural charisma means that he is in the top 5 for me, just a shame he seldom gets to 'showoff' his mic abilities.
6: Wade Barrett - Holy shit has anyone mentioned this guy yet? He seems to have been completely overlooked in this thread. He doesn't get a hell of a lot of time these days, but god dammit whenever he gets near a mic it's bloody brilliant. His voice is up there with Ambrose', it's so beautiful I could honestly just listen to it all day.
That's the top top ones at the moment, Christian and Rhodes would most certainly be the next two but I don't see them being in the list of 'The best mic workers', they are solid but nothing spectacular.